Coffee products which are in a form convenient for the consumer, are commonly available as soluble beverage powders and ready-to-drink liquid beverages.
Coffee products in the form of soluble beverage powders may be of extremely high quality; to the point were they provide a beverage very similar to freshly brewed beverages. Despite this, they are still perceived as being inferior to freshly brewed coffee. Also, the fact that soluble beverage powders are in powder form creates problems in many food service applications where the product is dispensed from a machine. In particular, problems such as mechanical degradation of the powder, bridging, and blocking occur.
Ready-to-drink liquid coffee beverages are very popular in Asian markets. The beverages are made up of soluble coffee solids, stabilizers, water and, usually, sugar. For whitened beverages, a creamer or whitener may be included. Ordinarily, these beverages have a soluble coffee solids concentration of about 1% by weight. These beverages are very often consumed cold and, in general, have organoleptic properties which are different than freshly brewed coffee. Therefore they do not and in fact are not intended to, provide a substitute to freshly brewed coffee.
There have also been attempts to provide convenient coffee products in fluid concentrate form. In theory, a coffee concentrate offers the advantages of being perceived to have better quality than soluble beverage powders, and being simple to apply in food service applications. Unfortunately, liquid coffee concentrates are unstable and this has severely limited their application. One problem appears to be the increase of acidity over time which negatively influences the quality of the beverage reconstituted from the coffee concentrate. Also, curdling of whitener or creamer components may occur.
Attempts have been made to avoid or reduce the acidity increase by adding base to the concentrate. For example, European patent application 0861596 describes treating a coffee concentrate with alkali to convert acid precursors to their acid salts, and then neutralizing the treated concentrate with acid to bring the pH to about 4.7 to 5.3. This process is described to convert the acid precursors to stable salts and hence prevent the formation of acid during storage.
Another possible method of avoiding or reducing the acidity increase in aromatized coffee concentrates is to increase concentration to above about 55%. This is described in European patent application 0893065.
These processes provide some improvement of the storage stability of the coffee concentrates, but quality deterioration still occurs. Therefore there is still a need for a stable coffee concentrate that overcomes these problems.